I have no idea of cost... I recall hearing the boat chips (with no security features) were $1.35ish per chip, on average (YMMV). Assume high value chips with security features are $8 per chip. I am perfectly happy selling a $1000 chip for $992 profit.
As would I. But I think casinos have a distinctly different viewpoint on this than you and me, and nothing to do with the cost to manufacture/acquire.
Value chips/checks represent a legal liability to the casino, fully and instantly redeemable for cash. I doubt they would want to lose, say, 5x $1000 chips per day for 6 months, and then all of a sudden one guy comes in and redeems $900,000 in chips all in one moment. It would be an uncomfortable situation for them (and, likely, the would-be redeemer as well).